The electrocatalytic characterization and mechanism of carbon nanotubes with different numbers of walls for the VO2+/VO2+ redox coupleElectronic supplementary information (ESI) available: Details of the metal impurities of received and purified CNT samples, the method and results of mathematical statistics on the distributions of the number of walls and outer diameter, the electrocatalytic results of CNTs-4 and oxidized CNTs-4 for the VO2+/VO2+ redox, the C1s core level XPS of CNTs-1, CNTs-3, CN

• Main Authors: Lv, Zhaoqian, Zhang, Jin, Lv, Yang, Cheng, Yi, Jiang, San Ping, Xiang, Yan, Lu, Shanfu
• Format: Article
• Language: English
• ISSN: 1463-9076; 1463-9084
• DOI: 10.1039/c7cp08683k

Carbon nanotubes (CNTs) have been applied as catalysts in the VO 2 + /VO 2+ redox, whereas the mechanism of CNTs for the redox reaction is still unclear. In this work, the mechanism of the VO 2 + /VO 2+ redox is investigated by comparing the electrocatalytic performance of CNTs with different distributions. For different CNTs, the peak current density of the VO 2 + /VO 2+ redox increases with increasing content of oxygen-functional groups on the surface of CNTs, especially the carboxyl group which is proved as active sites for the redox reaction. Moreover, the reversibility of the VO 2 + /VO 2+ redox decreases with increasing defects of CNTs, as the defects affect the charge transfer of the catalytic reaction. Nevertheless, when a multi-walled CNT sample is oxidized to achieve a high content of oxygen functional groups and defects, the peak current density of the redox reaction increases from 38.5 mA mg −1 to 45.4 mA mg −1 whilst the peak potential separation (Δ E p ) also increases from 0.176 V to 0.209 V. Overall, a balance between the oxygen functional groups and the defects of CNTs affects the peak current and the reversibility for the VO 2 + /VO 2+ redox. Remarkable differences in the electrocatalytic activity and reversibility were observed among CNTs with wall numbers for the VO 2 + /VO 2+ redox.